What is the function of a car knock sensor?

Detect engine knocking to suppress the occurrence of knocking phenomena. When the engineer adjusts the knock sensor, the vibration pattern of the knock is written into the electronic control unit. If the knock sensor detects a vibration pattern, the ECU determines the engine knock and then delays the ignition advance angle.

Currently, advanced knock sensors can even tell which cylinder is knocking and delay the ignition advance angle of that cylinder separately. 

The knock sensor is mounted in the middle of the engine block. For example, a four-cylinder engine is installed between cylinders 2 and 3, or one between cylinders 1 and 2 and one between cylinders 3 and 4. It is used to measure engine shake and adjust the ignition advance angle in case of engine knocking.

Usually piezoelectric ceramics. When the engine vibrates, the ceramic inside is squeezed to produce an electrical signal. Because this electrical signal is very weak, the connecting wires of ordinary knock sensors are wrapped with shielded wires.

Knock sensors are AC signal generators, but they are very different from most other AC signal generators in cars. In addition to detecting the speed and position of rotating shafts like magnetoelectric crankshaft and camshaft position sensors, they also detect vibration or mechanical pressure. Unlike stators and magnetoresistors, they are typically piezoelectric devices.

They are made of special materials that can sense mechanical pressure or vibration (for example, when the engine starts knocking, it can generate alternating voltage).

Engine damage can occur due to premature ignition, poor exhaust gas recirculation, and engine knocking caused by low-quality fuel. The knock sensor provides a knock signal to the computer, prompting the computer to readjust the ignition timing to prevent further knocking. They actually act as "oxygen sensors" in the ignition timing feedback control loop.

The working principle of the knock sensor: when the engine vibrates or knocks the cylinder, the piezoelectric ceramic produces a voltage peak, and the greater the knock or vibration, the greater the peak. The engine control unit (ECU) processes the signals received by the detonation sensor, and if a detonation is determined, the ignition is postponed and the detonation continues.

When the engine control unit ECU does not receive the signal from the knock sensor, the ignition time is advanced to ensure the optimal output of the engine. Therefore, the purpose of using a knock sensor is to improve the dynamic performance of the engine without knocking.

The knock sensor is installed in the middle of the engine block, and in the case of a four-cylinder engine, it is installed between the 2nd and 3rd cylinders, or 1

One in the middle of 2 cylinders, one in the middle of 3 and 4 cylinders. It is used to measure the degree of engine shake, and is used to adjust the ignition advance angle when the engine detonation.

There are many kinds of knock sensors, among which the earliest application is the magnetostrictive knock sensor, which is mainly composed of a magnetic core, a permanent magnet and an induction coil. When the body vibrates, the magnetic core is offset by vibration, which changes the magnetic flux in the induction coil and generates an induced electromotive force in the induction coil. Other types such as piezoelectric ceramics, when the engine is shaking, the ceramic inside is squeezed to produce an electrical signal, because this electrical signal is very weak, so the connection wire of the general detonation sensor is wrapped with shielded wire.

Knock sensors are AC signal generators, but they are very different from most other automotive AC signal generators, in addition to detecting the speed and position of the shaft like magnetoelectric crankshaft and camshaft position sensors, they also detect vibration or mechanical pressure. Unlike stators and magnetoresistors, they are usually piezoelectric devices. They are made of special materials that sense mechanical pressure or vibrations, such as alternating voltages when an engine detonation.

Engine knocking caused by premature ignition, poor exhaust recirculation, and low-grade fuel can cause engine damage. The knock sensor provides a knock signal to the computer (sometimes via a point-controlled modulus) so that the computer can readjust the ignition timing to prevent further knocking. They actually act as "oxygen sensors" that act as feedback control loops for ignition timing.

Knock sensors are placed in different positions on the engine block or cylinder. When vibration or cylinder knocking occurs, it produces a small voltage peak, the greater the cylinder knocking or vibration. The greater the peak of the knock sensor manufacturer.

A certain high frequency indicates knocking or knocking, and knock sensors are typically designed to measure frequencies in the range of 5 to 15 kHz. When these frequencies are received by the control unit, the computer recorrects the ignition timing to prevent further knocking, and knock sensors are usually very durable. So the sensor will only be damaged by its own failure.

When the engine knocks, a pressure wave is generated, the frequency of which is 1-10kHzThe pressure wave is transmitted to the cylinder block, causing the metal particles to vibrate and accelerate. The accelerometer knock sensor detects the strength of the knock pressure by measuring the vibration acceleration on the surface of the cylinder.

Premature ignition is a major cause of detonation. Due to the requirement that the engine can produce the maximum power, in order not to lose the engine power and not to produce detonation, a detonation sensor is installed to make the electronic control device automatically adjust the electric fire time.

In fact, a knock sensor is a piezoelectric element, and when it receives external pressure, the component generates a tiny electrical signal. When the cylinder is working, the detonation caused by spontaneous combustion will produce a strong vibration (like the sound of knocking on the cylinder), and the detonation sensor senses it, transmits it to the ECU in the form of an analog signal, and then adjusts the ignition time and the time of fuel injection 、、、 after calculation

A knock sensor is a component of a car. Common types: piezoelectric and ceramic telescopic. In order to prevent engine knocking due to engine load, temperature, fuel quality, excessive ignition time advance (ignition advance angle), etc.

It is to make the sensors work through the vibrations that occur in the car. The working principle is that when the car vibrates, the sensor will be triggered, and the sensor will start working.

The role and working principle of the automobile engine knock sensorThe role and working principle of the knock sensor, the knowledge of the goal, grasp the cause of the detonation (key), understand the role of the detonation sensor, master the structure and working principle of the detonation sensor (emphasis), the role and working principle of the detonation sensor, what is the detonation detonation, commonly known as knocking the cylinder and calling the rod. Detonation is an abnormal combustion phenomenon that occurs during the combustion of an engine. The role and working principle of the detonation sensor The characteristics of detonation:

1) Irregular metal knocking sounds of "clang", "click" and "dangdang" occur in the engine. (2) Engine tremor. (3) The engine temperature is too high.

4) The fuel burns incompletely, and there is black smoke in the exhaust gas. (5) Engine power decreases. (6) Increased fuel consumption.

7) During normal driving, the speed suddenly changes inexplicably. 2. Detection method of engine knocking There are three ways to detect engine knocking: detecting the change of engine combustion chamber pressure; Detect the vibration frequency of the engine block; Detection of combustion noise of gas mixtures.

The measurement accuracy of directly detecting the pressure change of the combustion chamber to detect engine vibration is high, but the sensor is difficult to install, and the durability is poor, so it is generally used for measuring instruments, and the pressure detection sensors in practical applications are indirect detection type.

Knock sensor: used to measure engine shake.

If the deflagration sensor is damaged, the engine control unit (ECU) is unable to monitor the degree of deflagration and thus mistakenly judge that no deflagration has occurred, in which case the engine control unit will increase the ignition advance angle, causing the engine to work violently due to deflagration.

When the engine control unit detects a deflagration of the engine through the deflagration sensor, the ignition advance angle will be reduced to avoid a strong deflagration when the deflagration sensor is intact.

Engine knocking is caused by an engine ignition advance angle that is too small; It can lead to engine shaking, decreased power torque, shortened engine life, etc.

Pursuing the smallest ignition advance angle is the perfect way to increase engine power.

If the ignition advance angle is too small, it will detonation, and too large will lead to insufficient power and increased fuel consumption.

In order to find the perfect ignition advance angle, a knock sensor is designed, and when a knock is detected, the ignition advance angle is increased to reduce the detonation. Find the best ignition advance angle through repeated attempts; This is also a mandatory part of the vehicle's self-learning process.

Automotive sensors, which used to be used solely in engines, are now being used in chassis, body, and lighting electrical systems. These systems use more than 100 sensors. Among the wide variety of sensors, the common ones are inlet pressure sensors:

Reflects the change in the absolute pressure in the intake manifold and provides a reference signal to the ECU (Engine Electronic Control Unit) to calculate the duration of the injection. Air flow meter: measures the amount of air inhaled by the engine and provides it to the ECU as a reference signal for the injection time; Throttle position sensor: measure the angle of throttle opening, and provide ECU as a reference signal for oil cut-off, control of fuel-air ratio, and ignition advance angle correction; Crankshaft position sensor:

Detect the crankshaft and engine speed, and provide it to the ECU as a reference signal to determine the ignition timing and working sequence;

What is an engine erection super knock.

Engine "super knocking", also known as low-speed premature ignition, is an abnormal combustion phenomenon unique to supercharged direct-injection gasoline engines. When the engine inhales the mixture of fuel vapor and air, in the process of compression, due to the mixture of low ignition point substances in the fuel, it will cause the gas mixture to automatically deflagrate before the ignition of the spark plug, forming a new ignition point, and the flame spreads outward at a speed several times higher than the normal combustion, so that the cylinder wall is affected and vibrates, which is called detonation. To put it simply, knocking is a manifestation of abnormal pressure in the combustion chamber caused by abnormal combustion.

A phenomenon when detonation occurs.

The engine will emit a crisp and discontinuous metal knocking sound when a slight knock occurs, while a continuous metal knocking sound will occur when the engine will have a continuous metal knocking sound during a severe and continuous knock, and the engine power will also be significantly reduced.

What are the causes of the explosion?

1 The air-fuel ratio is incorrect, and the mixture is too dilute to increase the combustion temperature, thereby increasing the engine temperature.

2. The octane number of fuel is too low, the octane number is an indicator of anti-detonation, the higher the octane number, the stronger the anti-detonation, and the lower the conversely, it is easy to detonation.

3. The cleanliness of the fuel is insufficient, and some physical substances and chemical impurities contained in the fuel, including some aromatic substances, will cause spontaneous combustion and detonation during the compression process of the engine.

4. Excessive carbon deposition in the combustion chamber, due to the serious carbon deposition, the actual volume of the cylinder becomes smaller, the compression ratio increases, and at the same time, the carbon deposition in the high-temperature environment will always burn red due to poor heat dissipation ability, so that the high-temperature compressed mixture is not only ignited by the spark plug of the timing judgment, but also randomly ignited by the high-temperature carbon deposition in the cylinder, resulting in detonation.

5. The engine temperature is too high, the engine is too hot in the environment, the inlet air temperature is too high, or the engine cooling water circulation is poor, which will cause the engine to detonate at high temperature.

6 The ignition angle is too early, so that the piston can gain power as soon as it enters the power stroke after the compression stroke is completed, it is usually ignited before the piston reaches the top dead center. Ignition too early will cause most of the oil and gas to burn when the piston is still compressing the stroke, and the unburned oil and gas will be subjected to great pressure and spontaneous combustion, resulting in detonation.

The methods to solve detonation are as follows.

1. Use fuel that conforms to the compression ratio of the engine.

2. Avoid "drag gear" driving.

3. Regularly clean the carbon deposits and fuel injectors in the oil circuit.

4. Avoid high temperatures: check the coolant water level regularly, check and change the engine oil regularly, avoid long-term intense driving, and monitor the water temperature frequently when driving in summer.

5. Appropriate selection of high-quality fuel additives. For example, fuel additives containing PNF stock solution can solve the problem of engine knocking to a certain extent.

Knock sensor: used to measure engine shake.

1. Knock sensors are AC signal generators, but they are very different from most other automotive AC signal generators, in addition to detecting the speed and position of the rotating shaft like magnetoelectric crankshaft and camshaft position sensors, they also detect vibration or mechanical pressure. Unlike stators and magnetoresistors, they are usually piezoelectric devices.

2. They are composed of special materials that can sense mechanical pressure or vibration (such as AC voltage can be generated when the engine detonation);

3. Premature ignition, poor exhaust recirculation, low-grade fuel and other reasonsEngine knocking can cause engine damage. The knock sensor provides a knock signal to the computer (sometimes via a point-controlled modulus) so that the computer can readjust the ignition timing to prevent further knocking.